Easy opening container with safety edge compounds

ABSTRACT

Easy open containers, particularly those of the full-panel type, having safety edge compound applied to the scored metal area of the end are provided whereby, upon pulling the tab to open the container, the compound tears at the score line with a portion remaining on the metal edge of the removable panel as well as on the container rim giving protection to the consumer against cutting on raw metal edges to the ends thus treated.

United States Patent Rentmeester et al.

[4 1 May 13, 1975 1 1 EASY OPENING CONTAINER WITH SAFETY EDGE COMPOUNDS[75] inventors: Kenneth Richard Rentmeester,

Barrington; Joseph Lambert Godar, Jr., Wauconda, both of 111.

[73] Assignee: American Can Company,

Greenwich, Conn.

[22] Filed: Sept. 19, 1973 [21] Appl. No: 399,123

[52] US. Cl. 220/270; 113/121 A; 220/906 [51] Int. Cl. B65d 41/32 [58]Field of Search 220/54, 53, 90.6, 27, 266, 220/270; 113/121 A [56]References Cited UNITED STATES PATENTS 3,754,678 8/1973 Fox et a1 220/54Hekal et al. 220/54 Kehe 220/54 Primary E.\-aminerGeorge T. HallAttorney, Agent, or Firm-Robert P. Auber; Ernestine C. Bartlett; GeorgeP. Ziehmer [57] ABSTRACT 18 Claims, 3 Drawing Figures EASY OPENINGCONTAINER WITH SAFETY EDGE COMPOUNDS BACKGROUND OF THE INVENTION Thisinvention relates to containers and in particular to new and improvedeasy opening ends for containers.

Heretofore metallic containers have been provided with easy-openingmeans to facilitate the emptying of the contents therefrom. These priorstructures have been generally characterized by a structure in which atear portion defined by a scored line in the container is separated fromthe container. Although such easy opening containers have been readilyaccepted by the public, several disadvantages have made their use lessthan totally satisfactory. Perhaps the major disadvantage has beeninsufficient protection of the raw, sharp metal edges which result whenthe removable portion is torn from the end.

Many proposals have been made in the can making industry to solve theproblems presented by the unprotected raw metal edges of suchcontainers. Many of such proposals include application of plastisols tothe score area of the removable portion so that when the can end isopened, the plastisol will separate along the score line with a portionremaining on the end in the areas of the score line which serves toprotect, to a certain extent, the raw metal edge thereby diminishing thelikelihood of being cut. Plastisol materials proposed as safety edgecompounds are basically vinyl chlorideresin containing suspensions innon-aqueous liquids which do not dissolve the resin at ordinarytemperature, such liquids normally being plasticizers. Such suspensionscan be converted to films by heating to approximately 340 F to above 380F depending upon the type of plasticizer used. While the use ofplastisols has afforded some protection from raw metal edges, suchcompounds are totally unsatisfactory for many applications.

A satisfactory safety edge compound should desirably possess thefollowing properties for broad application and use; particularly forcontainers packed with edible goods:

1. Resistance to edible fats and oils.

2. Suitable extractive levels required by the FDA for food contactsurfaces, i.e., insolubility in common solvents such as water, alcohol,etc.

3. Resistance to heat thereby achieving acceptance for aseptic containersteam sterilization and thermal heat processing of the packed products.

4. Good adhesion to the various types of resinous coated substrates aswell as to laminate and/or unprimed substrates.

5. Curing and drying at low temperatures for easy and economicalmanufacture.

6. Ready application through conventional equipment and simplicity ofmanufacture.

7. Satisfactory physical properties, for example, elongation, tensilestrength, tear strength, etc. to permit the compound to tear cleanly,i.e., without fragments, stringing and frills when the container isopened.

Plastisols are decidedly deficient in many of the above mentionedcriteria particularly where the container is to be packed with ediblegoods. For example, plastisols, in general, do not meet FDA extractivelevels, do not possess resistance to heat and moisture encountered underaseptic processing conditions and require specific primers for adhesionto substrates. Moreover, plastisols require special equipment for theirmanufacture, heavy duty pump equipment for application and hightemperature curing ovens (they generally require temperatures above 380F for adequate curing) and once applied, the compositions frequentlyfragment or frill when the container is opened, and become mobile duringaseptic sterilization.

Elastomeric polymers, sometimes referred to in the art as rubbersealants have long been known in the art as excellent gasketing and endlining materials resulting in tough gaskets or seals having resistanceto fat and oils, usually conveyed by inclusion of organicsolvent-insoluble rubbers and resistance to moist heat, usually conveyedthrough use of a tackifying resin. Such compositions are disclosed andclaimed in U.S. Pat. No. 2,767,152, for example, and usually include asolvent-soluble rubber in combination with a solventinsoluble rubber,tackifying resin and filler, diluted with solvent to proper viscosity,to a solids content usually between about 34 to 40%. Such compositionsare not suitable for use as safety edge compounds as illustrated furtherhereinbelow because they are normally too highly elongated resulting instringing or frilling when the structure is torn. Additionally, thetackifying resin necessarily present in gasketing or lining compounds toprevent deterioration and afford moist heat resistance, when employed ina safety edge compound inhibits drying of the film, causes blocking andsticking and'other problems.

The primary object of this invention is to provide an improvedeasy-opening container with a safety feature which protects the rupturedscore edge of the removable section as well as the metal edge remainingon the container.

Another object of the invention is to provide an easyopening containerhaving protected metal edges employing safety edge compounds whichpossess all of the advantages above enumerated including resistance tofats and oils, resistance to heat, good adhesion to a variety ofsubstrates, coated and unprimed, and proper elongation and tearproperties.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description, which, takenin connection-with the accompanying drawing, discloses a preferredembodiment thereof.

SUMMARY OF THE INVENTION This invention relates to an easy-openingcontainer, preferably of the type having a full-open and closure seamedto a container body, wherein the end closure includes a peripheralcountersink wall, a full-open removable central panel section defined bya peripheral score, an opening tab secured to the central panel andoperative upon manipulation to impress an opening force to cause arupture in the score, to leave a rim between the countersink wall andthe score. The improvement comprises providing a safety edge compound,comprising elastomeric polymer compounded with suitable fillers, on thescore line to protect the metal edges upon rupturing the score.

Brief Description of the Drawing FIG. 1 is a top plan view of an endclosure of an easyopen container of this invention.

FIG. 2 is an enlarged fragmentary vertical section taken along line 22of FIG. 1.

FIG. 3 is an enlarged fragmentary sectional view similar to FIG. 2showing a portion of the removable central panel section removed fromthe container body.

DETAILED DESCRIPTION OF THE INVENTION As a preferred and exemplary formof the present invention, FIG. 1 shows a cylindrical can C having aconventional top end closure having a central wall 12 defined by asubstantially peripheral primary score line 14, which defines aremovable central panel 24 that includes most of central wall 12, aperipheral secondary score line 15, a rim 16 which merges into anupwardly extending annular countersink wall 18 (FIG. 2) and an annularflange 20 interfolded with the upper end portion of a container body Cinto a double seam 22 (FIG. 2).

Central panel 24 has an opening tab 26 secured thereto by conventionalmeans, for example, a rivet 28. The opening tab, as illustrated in FIG.1, has a front portion 30 at one end adjacent score line 14 and a handleportion 32 at the other end. The front portion 30 at one end adjacentscore line 14 in this embodiment includes a web portion 36 having aU-shaped slit cut 38 therethrough which defines a flap 40 wherein islocated the hole in which rivet 28 is secured. The major portion offront end portion 30 lies outside of U-shaped slit cut 38 so that whenhandle 32 is lifted upwardly, the front end portion 30 and the rest oftab 26 are free to pivot about rivet 28 to allow nose 34 to rupturescore line 14, while flap 40 is held flatly against central panel 12 byrivet 28. The opening tab as illustrated is described only as a specificembodiment herein and it should be understood that other suitable formsof the opening tab may be substituted.

To facilitate opening and easy initial rupture of the primary score 14,a secondary score may be formed in the central panel although theinvention is equally applicable to structures devoid of such anauxiliary score.

As best seen in FIGS. 2 and 3, a safety edge compound 46 comprising anelastomeric polymer is present on the undersurface of removable panelsection 24 adjacent and covering score line 14 (and score line 15 ifpresent) to protect the edge of the panel section 24 and the rim 16 oncethe score is ruptured and panel 24 is partly or fully removed from riml6 and container body C. As shown in FIG. 3, the safety edge compoundcovers the rim l6 and score lands 42 and 44 so that should the scorerupture with all or a portion of the land remaining with central panel24 or rim 16, there remains on all edges a protective elastomeric edge.

The compositions employed as safety edge compounds according to theinvention consist essentially of elastomeric polymer materialscompounded with suitable fillers.

Typical safety edge compounds of the invention will have the followingcomposition:

Percent By Weight -Continued Solid Ingredients Percent By Weight 45-75%pre- 55-25%, pmferably about ferably about 50-60% 50-40% To achieve thedesired results herein, the relative proportions of the componentsshould be maintained within the stated ranges. For example compositionscontaining substantially less than 5% elastomeric polymer result incompounds that are too friable for the purposes of the invention whilethose containing substantially more than 30% elastomer or less thanfiller are too stringy for satisfactory use both as a safety edgecompound and in conventional nozzle equipment. Similarly, when theingredients are compounded to have a solids content substantially lowerthan about 45%, the solution is too thin for satisfactory application.Substantially above solids, the compounds are too viscous for readyapplication.

The elastomeric polymer component of the compounds of the invention arewell known in the art and include butadiene-acrylonitrile copolymers,butadienestyrene copolymers, isobutylene-isoprene copolymers, Naturalrubber (polyisoprene), ethylene-propylene copolymer, neoprene,polyacrylic rubber, chlorosulfonated polyethylene (I-Iypalon), etc. andmixtures thereof. Expecially preferred are mixtures of solubleelastomers, particularly those including butadieneacrylonitrile polymerscontaining about 50 to about 70 percent by weight butadiene and about 30to 50 percent acrylonitrile. An example of such a copolymer which iscommercially available and suitable for use in the present invention isHycar 1001 available from the B. F. Goodrich Chemical Company. Anexample of a suitable butadiene-styrene copolymer is Kraton l 101available from Shell Chemical Company while a suitableisobutylene-isoprene polymer is Butyl O07 available from Exxon ChemicalCompany. Especially preferred for use herein are mixtures of organicsolventsoluble polymers such asbutadiene-acrylonitrile/isobutylene-isoprene andbutadiene-styrene/isobutyleneisoprene. While the above elastomersconstitute preferred embodiments of the invention, it should beunderstood that other elastomeric polymers may be substituted thereforprovided they are soluble in an organic solvent and, when compoundedaccording to the invention, exhibit suitable elongation, tear andtensile strengths to tear cleanly and evenly without fragmenting,frilling or stringing.

The filler component of the compounds of the invention is likewiseselected from compounds well known in the art and includes titaniumdioxide, silica, zinc oxide and other fillers that function inaccordance with the present invention. Especially preferred are highdensity (3 or above) nonreinforcing type fillers which form compoundswith the elastomer having adequate tear properties. Such components maybe employed alone, in combination with each other or with other fillersand/or pigments well known in the art.

The liquid medium or vehicle employed herein may include suitablesolvents or diluents which may be selected to form solutions,dispersions, etc., based on the solubility of the particular polymer,ease of drying and ecological properties, as desired. Thus, the vehiclemay include water, organic and inorganic solvents, diluents andcombinations thereof. Particularly preferred I added to the vehicle,with or without milling as deemed necessary after which the elastomerswill be added, preferably with agitation to aid in solvation ordispersion of the same.

In a typical procedure of the process, metal sheet, which may bealuminum, tinplate, tin-free steel, etc., is coated with typical primercoatings which may be any of a variety of conventional coatingsincluding oleoresinous lacquers or enamels such as tung oil or linseedoil based materials, epoxy esters, epoxy-phenolics, acrylics, vinyls,etc. The primed sheet is formed into the basic end and converted to aninside or outside scored full-panel, easy-open end by any ofconventional procedures known in the art. A safety edge compound of theinvention is applied to the score area by any suitable means, employingpreferably conventional nozzle equipment, and is dried to evaporate atleast a portion of the vehicle, utilizing standard equipment, forexample, a helical dryer, at a temperature of about 100 to 180 F,preferably about 130 F for about 6 minutes. Complete cure of thecompound is not necessary so long as sufficient vehicle is removed topreserve the integrity of the compound whereby it can serve the desiredfunction.

The primary score land may be of any length desired,

generally from about 0.001 to 0.005 inch and may be formed by either aninside or outside score. The secondary score depth, when present, willbe substantially less than that of the primary score, normally about0.003 inch or less and likewise may be on the interior or exteriorsurface of the end.

Thicknesses of the safety compounds may vary as desired and preferablywill be in the range of about 4 to 25 mils with 8 to mils being thepreferred range. The width of the compound as applied likewise may varyas desired, usually from about a one-eighth inch minimum to as wide asdesired and as is economically feasible. The compound may or may not beapplied to cover the secondary score, as desired although it will bepreferably cover both the primary and secondary score in the practice ofthis invention. Similarly, the compound may be applied to the interioror exterior surface of the end with interior application being mostpreferred herein.

The following examples are illustrative of various compositions suitablefor use in this invention:

EXAMPLE ll Ingredients Percent by Weight butadieneacrylonitrile l 1.0copolymer (Hycar 1001) isobutylenc-isoprene 0.5 copolymer Butyl 007) TiO11.0 SiO- 32.5 Toluene/Methyl ethyl ketone 45.0

The following examples are illustrative of elastomeric compositionsknown in the art of gasketing or sealing compounds, which are notsatisfactory as safety edge compounds in accordance with this invention.

EXAMPLE III This formulation is as disclosed in US. Pat. No. 2,767,152to Biermann:

The above formulations (Examples I to IV) were applied to a primed,scored, metal end in accordance with the invention and dried at F forabout 6 minutes or until a substantial amount of vehicle was evaporated.The compositions of Examples 1 and II had a solids content of about 55percent while that of Examples 111 and IV was about 36 percent.

The compounds of Examples 111 and IV were found to be totallyunsatisfactory for use as a safety edge compound. Drying was inhibitedby the tackifying resin in each case necessitating at the least doublingof drying time. Upon rupturing the score line, the compounds of each ofthese examples were excessively stringy and were found to be too soft togive raw edge protection. Additionally, ends containing compounds ofthese examples were extremely difficult to process because of thetackiness of the compounds which caused blocking or sticking of the endsone to the other.

The compounds of Examples 1 and II were not tacky, did not block,provided excellent protection to the metal edges, tearing cleanly andeasily without stringing, fragmenting or frilling and exhibited goodretention of adhesion to the metal ends even when opened at vendingtemperatures of 150 F or higher. The compound of Example l isparticularly well suited for use on container ends under asepticconditions while the compound of Example II is the preferred fatresistant compound.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the matter of theingredients, the identity and proportions of the formulation and thatchanges may be made in the form, construction and arrangement of theparts of the article without departing from the spirit and scope of theinvention or sacrificing all of its material advantages, the formhereinbefore described being merely a preferred embodiment thereof.

We claim:

1. In a metal container wherein a full-open end closure is seamed to acontainer body, wherein the end closure includes a peripheralcountersink wall, fullopen removable central panel defined by asubstantially peripheral score line and an opening tab secured to thecentral panel and operative upon manipulation to cause a rupture in thescore to leave a rim between the countersink wall and the score, theimprovement which comprises:

a safety edge compound having sufficient elongation,

tear and tensile characteristics to tear without substantial fragmentingor stringing upon removal of the central panel derived from acomposition comprising from about to about 30 percent of an elastomericpolymer, liquid vehicle and from about 95 to 70 percent filler, saidcompound covering the score and tearing to protect the metal edges ofthe removable panel section and the rim upon rupture of the score.

2. The container of claim 1 wherein the compound is applied to theinterior surface of the scored end.

3. The container of claim 1 wherein the composition has a solids contentof about 45 to about 75 percent.

4. The container of claim 3 wherein said elastomer is selected from thegroup consisting of copolymers of butadiene-acrylonitrile,butadiene-styrene, isobutylene-isoprene, ethylene-propylene,polyisoprene, neoprene, polyacrylic rubber, chlorosulfonatedpolyethylene and mixtures thereof.

5. The container of claim 4 wherein said elastomer is a mixture ofbutadiene-acrylonitrile and isobutyleneisoprene copolymers.

6. The container of claim 4 wherein said elastomer is a mixture ofbutadiene-styrene and isobutyleneisoprene copolymers.

7. The container of claim 1 wherein said filler is titanium dioxide,zinc oxide, silicon dioxide and mixtures thereof.

8. The container of claim 1 wherein said elastomer is a mixture ofbutadiene-acrylonitrile and isobutyleneisoprene copolymers, said filleris a mixture of titanium dioxide and silicon-dioxide and said vehicle isa methyl ethyl ketone-toluene mixture.

9. The container of claim 1 wherein said elastomer is 5 a mixture ofbutadiene-styrene and isobutyleneisoprene copolymers, said filler is amixture of titanium dioxide and silicon dioxide and said vehicle is atoluene-hexane mixture.

10. The container of claim 1 wherein said compound is derived byevaporation of at least a portion of the vehicle from said compositionafter application to the metal end.

11. The container of claim wherein said compound is derived by heatingsaid composition to a temperature of about 100 F to about 180 F.

12. A method for making an improved, full-open end closure comprising,in combination:

a. forming a can end, including a peripheral countersink wall and flangemeans to be seamed to the end of a container body,

b. forming a score line in said end, said score line defining aremovable central panel portion which is separable from a rim in saidcountersink wall of said end,

c. attaching finger tab means to a portion of said removable centralpanel portion,

d. applying to said score line a composition comprising an elastomericpolymer, liquid vehicle and filler and e. removing at least a portion ofsaid vehicle to provide a cured compound which protects the metal edgesof the removable central panel portion and the rim upon rupture of thescore.

13. A method as defined in claim 12 in which said composition is appliedto the interior surface of the scored end.

14. A method as defined in claim 12 wherein the compound consistsessentially of from about 5 to about 30 percent by weight of anelastomeric polymer or mixtures thereof, and from about 70 to about 95percent by weight of a filler.

15. A method as defined in claim 14 wherein the composition has a solidscontent of about 45 to about 75 percent.

16. A method as defined in claim 15 wherein said elastomer is selectedfrom the group consisting of copolymers of butadiene-acrylonitrile,butadiene-styrene, isobutylene-isoprene, ethylene-propylene,polyisoprene, neoprene, polyacrylic rubber, chlorosulfonatedpolyethylene and mixtures thereof.

17. A method as defined in claim 16 wherein said filler is titaniumdioxide, zinc oxide, silicon dioxide and mixtures thereof.

18. A method as defined in claim 17 wherein said cured product isprovided by baking said end at a temperature of about 100 F to about 180F.

1. In a metal container wherein a full-open end closure is seamed to acontainer body, wherein the end closure includes a peripheralcountersink wall, full-open removable central panel defined by asubstantially peripheral score line and an opening tab secured to thecentral panel and operative upon manipulation to cause a rupture in thescore to leave a rim between the countersink wall and the score, theimprovement which comprises: a safety edge compound having sufficientelongation, tear and tensile characteristics to tear without substantialfragmenting or stringing upon removal of the central panel derived froma composition comprising from about 5 to about 30 percent of anelastomeric polymer, liquid vehicle and from about 95 to 70 percentfiller, said compound covering the score and tearing to protect themetal edges of the removable panel section and the rim upon rupture ofthe score.
 2. The container of claim 1 wherein the compound is appliedto the interior surface of the scored end.
 3. The container of claim 1wherein the composition has a solids content of about 45 to about 75percent.
 4. The container of claim 3 wherein said elastomer is selectedfrom the group consisting of copolymers of butadiene-acrylonitrile,butadiene-styrene, isobutylene-isoprene, ethylene-propylene,polyisoprene, neoprene, polyacrylic rubber, chlorosulfonatedpolyethylene and mixtures thereof.
 5. The container of claim 4 whereinsaid elastomer is a mixture of butadiene-acrylonitrile andisobutylene-isoprene copolymers.
 6. The container of claim 4 whereinsaid elastomer is a mixture of butadiene-styrene andisobutylene-isoprene copolymers.
 7. The container of claim 1 whereinsaid filler is titanium dioxide, zinc oxide, silicon dioxide andmixtures thereof.
 8. The container of claim 1 wherein said elastomer isa mixture of butadiene-acrylonitrile and isobutylene-isoprenecopolymers, said filler is a mixture of titanium dioxide andsilicon-dioxide and said vehicle is a methyl ethyl ketone-toluenemixture.
 9. The container of claim 1 wherein said elastomer is a mixtureof butadiene-styrene and isobutylene-isoprene copolymers, said filler isa mixture of titanium dioxide and silicon dioxide and said vehicle is atoluene-hexane mixture.
 10. The container of claim 1 wherein saidcompound is derived by evaporation of at least a portion of the vehiclefrom said composition after application to the metal end.
 11. Thecontainer of claim 10 wherein said compound is derived by heating saidcomposition to a temperature of about 100* F to about 180* F.
 12. Amethod for making an improved, full-open end closure comprising, incombination: a. forming a can end, including a peripheral countersinkwall and flange means to be seamed to the end of a container body, b.forming a score line in said end, said score line defining a removablecentral panel portion which is separable from a rim in said countersinkwall of said end, c. attaching Finger tab means to a portion of saidremovable central panel portion, d. applying to said score line acomposition comprising an elastomeric polymer, liquid vehicle and fillerand e. removing at least a portion of said vehicle to provide a curedcompound which protects the metal edges of the removable central panelportion and the rim upon rupture of the score.
 13. A method as definedin claim 12 in which said composition is applied to the interior surfaceof the scored end.
 14. A method as defined in claim 12 wherein thecompound consists essentially of from about 5 to about 30 percent byweight of an elastomeric polymer or mixtures thereof, and from about 70to about 95 percent by weight of a filler.
 15. A method as defined inclaim 14 wherein the composition has a solids content of about 45 toabout 75 percent.
 16. A method as defined in claim 15 wherein saidelastomer is selected from the group consisting of copolymers ofbutadiene-acrylonitrile, butadiene-styrene, isobutylene-isoprene,ethylene-propylene, polyisoprene, neoprene, polyacrylic rubber,chlorosulfonated polyethylene and mixtures thereof.
 17. A method asdefined in claim 16 wherein said filler is titanium dioxide, zinc oxide,silicon dioxide and mixtures thereof.
 18. A method as defined in claim17 wherein said cured product is provided by baking said end at atemperature of about 100* F to about 180* F.